Meanwhile, authorities planned to spend a fourth day scouring photographic and video evidence for signs of what happened in the moments leading up to the explosions.

Two suspects have been singled out from department store surveillance footage, authorities told the Los Angeles Times. But despite a frenzy of conflicting media reports Wednesday, officials had not made any arrests in the bombings that revived memories of the terrorist attacks on the World Trade Center and the Pentagon on Sept. 11, 2001.

Attorney Kenneth Feinberg, a Massachusetts native who oversaw the 9/11 victims compensation funds, will arrive in Boston on Friday to head a fund created to help bombing victims.

By Wednesday evening, companies and individuals had committed $7 million to The One Fund Boston.

“We are humbled by the outpouring of support we’ve received over the past few days,” Boston Mayor Thomas Menino said in a statement. “The world stands with the City of Boston during this difficult time.”

Maeve Reston in Los Angeles and Richard A. Serrano in Washington contributed to this report.